Heart of a Phantom
by EternalRandomChick
Summary: Post-PP. All is going well in Amity Park. Ever since the Disasteroid incident, the ghosts have more or less left the town alone until strange creatures arrive, followed soon by even stranger warriors. This will be one of Danny's greatest fights ever against the ultimate enemy. Pairings in canon with their own universes.
1. The Heartless Attack

**A/N: Hello, and welcome to my first contribution to the Danny Phantom fandom. Okay, I know that this is a crossover between DP and Kingdom Hearts, but I think that, if DP belonged to Disney, we would hopefully be seeing some stuff from the show in that video game. I know that one similar to this has already been done, but I'm just warming up. This will go much differently that the other person's, I promise you that.**

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Chapter One: The Heartless Attack

For most of the people in Amity Park, it was just another night. The people were still getting used to the peace and quiet which had followed in the days after the Disasteroid incident. There had been no ghost attacks ever since, and their own protector Danny Phantom had been hailed as a hero all over the world, and the citizens of Amity Park were especially proud of the statue erected to the world hero in their city. Yes, duplicates of the statue stood all over the world, but this statue resided in the hero's hometown, and that was something for that town to be proud of.

Even now, a month after the apocalypse had been avoided; the citizens of Amity Park knew that they were safe. A sense of security had settled over the town, a sense that had only grown over time while the town was under the protection of the ghost boy. And this night, several people stuck their heads out the windows and waved to their hero as he patrolled the city.

"How do things look from your perspective, guys?" Danny asked his friends through the Fenton phones. "Everything still calm?"

"Looks the same as last night, and the night before, and the night before," Tucker reported. "You have to admit, dude, patrolling has been pretty much doze-ville ever since the Disasteroid."

"Very true, but you never know when a ghost could attack; this _is_ Amity Park, after all." Danny replied. "And I'd like to take care of any problems before they spread and become too tough to deal with. How are things looking on your side Valerie?" The Red Huntress had joined Team Phantom after finding out that the ghost boy and her friend were the same person.

"If there were any ghosts around, they'd be back in the Ghost Zone before the Box Ghost could say 'Beware'!" Valerie laughed, but then she became serious. "Same thing as Tucker reported; everything's calm on this end of town."

"Sam? How do things look at the park?" Danny sounded a little worried, and the other two members of Team Phantom couldn't help but snicker. Danny had always been somewhat protective of the dark and brooding girl, and that protectiveness had only increased after the Disasteroid since the ghost boy and the Goth girl had become an official couple. Not that that was surprising, everyone expected they would end up together; it was only a matter of time before Danny got over his usual cluelessness and realized his feelings for her.

"For the most part, it's all calm, but there was a weird shadow thing here a few minutes ago. I was following it, but I lost it just before you asked us to report in." The Goth reported.

"We'd better check it out, guys." Danny decided, immediately turning around and flying towards the park.

It did not take Danny long to find Sam, and Tucker and Valerie joined them moments later. "Where did you see this shadow? Well, where was it when it disappeared?" Tucker asked.

"Over there," Sam pointed to one of the trees. Danny shuddered. The place she was pointing to was frighteningly close to where that huge tree of Undergrowth's had been when Danny had returned from developing his ice powers.

"Are you sure, Sam?" Tucker said condescendingly. "It's nighttime, of course there's going to be shadows."

Sam turned to the techno-geek with a growl. "Tucker, do I need to remind you that I'm wearing _combat boots_? More importantly, do I need to _enforce_ said combat boots?"

Tucker shrank away from the angry Goth. "No." he said in a frightened whisper.

"Good." Sam turned back to the tree at which she had pointed. "This shadow was moving. I first saw it at the fountain and I followed it to right around here, but then I got distracted when you asked for the report of our patrols."

"Do you think Johnny 13 could be causing trouble again?" Danny asked.

"I didn't see him, or any other ghost for that matter." Sam informed her boyfriend. "And besides, that thing looked too small to be his shadow."

"Well then, could Undergrowth have something to do with it?" Danny asked, going up to the tree and investigating the ground. "I know that sounds highly unlikely, but this tree is pretty close to where that huge tree of his grew."

Sam blanched and shuddered, remembering what she called the horror stories of what she had done to Danny while under Undergrowth's control. "Let's hope not. I really don't want to become his 'queen' again."

"Could it be Nocturn, then?" Tucker suggested. "If I remember that incident correctly, those Sleepwalkers of his loved sinking into the ground and then leaping up to grab you and putting you to sleep with those stupid helmets so that Nocturn can absorb the energy from your dream."

Both Sam and Danny blushed, remembering that, during the Nocturn incident, they had both had the same dream. "Unless Nocturn's managed to upgrade his Sleepwalkers to a more dangerous level, it's not him." Sam informed the techno-geek. "This thing was small, black, quiet, had big, glowing, yellow eyes, and extremely strange antenna. As we remember well from the Nocturn incident, the Sleepwalkers are green, fairly large, make that creepy moaning sound, had eyes that looked like they were sewn shut, and did not have antenna."

Valerie suggested that the creature might be something that Vlad sent, but that theory was instantly shot down by Danny, who said that Vlad was too much of a fruit-loop, and besides, the Wisconsin Ghost hadn't been seen since Danny's father had abandoned the traitor in space.

But unknown to the team, a figure, shrouded in shadow, was watching them from a distance. He was a ghost, but he was such a master of evil and darkness that he was the only ghost, besides Spectra, who could mask his presence from Danny's ghost sense. The only feature of his that could be seen were his glowing blood-red eyes. A sadistic grin crossed his face as he pointed at the group, and multiple creatures of the same sort that Sam had seen earlier came out of the ground and surged towards the heroes.

All members of Team Phantom gasped when they were surrounded by shadow creatures. Most of them were small, but there were some that were larger than the rest, and these had some form of armor protecting them.

"Now do you believe me?" Sam yelled at Tucker.

"Looks like he brought a few friends with him!" Valerie growled.

"Alright, gang. Let's DO THIS!" Danny shouted, letting loose a few ecto-blasts as the group charged into battle.

The fight started out going well enough for Team Phantom; the ecto weapons proving to be very effective against this strange new enemy. At least, that's what appeared to be the case at first. While the wrist-rays, ecto-guns and ecto-blasts looked to be doing serious damage, after a while, the creatures would simply get back up again, moving as if absolutely nothing had happened. And with every time they got back up, they seemed to have also gotten stronger. And there were also more of them approaching with every pass.

"What ARE these things?" Valerie asked; shooting her ecto-gun to her heart's content at the monsters.

"No idea." Danny confessed, firing ecto-blast after ecto-blast. "But I have a sneaking suspicion that they're not ghosts."

After ten minutes that felt like ten hours, the creatures suddenly vanished. "What?" Sam asked. "But they had the upper hand; why would they just retreat?"

"Hey, don't complain about it!" Tucker exclaimed. "Whoever sent those things might hear you, think you're complaining about the retreat, and send even more!"

"Not likely, Tuck," Danny said, spinning in the air to try to see if there were any more creatures left, or if he could spot whoever they were controlled by. "I can honestly say that I have absolutely no idea what those things really wanted or why they retreated," he addressed the entire group as he landed. "But I would like to know exactly what those creatures were and who was controlling them. Forces that have the upper hand don't just retreat when they're acting on their own; they were called back by something or someone. It would be nice to know exactly who and what we're up against."

"Consider it done." Valerie promised. "We'll meet up at the Nasty Burger tomorrow at noon to discuss the results of our research."

"Val, we'd meet up there anyway." Tucker pointed out not so helpfully.

"Well, now we have even more of a reason to meet up there, instead of to just hang out." She giggled at the pouting look that appeared on Tucker's face when she said that and continued. "Don't get me wrong, Tuck, hanging out's fun, but what with us being ghost hunters, there are going to have to be days when we discuss research and strategy, not just have a laugh about kicking some ghost's butt."

"My only regret is that we didn't get a picture of one of those things." Sam growled.

"Who says we didn't?" Tucker asked, proudly showing a picture of one of the unarmored ones on his PDA.

Sam gasped, grabbing Tucker's PDA so that she could get a better look. "Tucker, I know I don't say this often," she laughed, "but you're a genius!"

"Yeah, way to go, dude!" Danny complimented, flashing his friend the thumbs-up. He took the PDA from Sam to get his own look at one of their attackers before handing the device back to the techno-geek. "I have a feeling that most of our information tomorrow is gonna come from you. Email that picture to all of us and we'll see what we can find out."

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**A/N: That space for reviews isn't going to fill itself (Hint, hint. Wink, wink. Snake in the grass, watch out!)**


	2. Help Has Arrived

**A/N: Wow, you guys were more interested in this story than I expected! Well, anyway, here's the second chapter. I think I'm moving a bit too fast; let me know if I'm doing that, please?**

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Chapter Two: Help Has Arrived

As they had expected, by the time of their afternoon meeting, Tucker was the one who had found out the most about their mysterious little visitors. Actually, he was the only one who really had any information that would possibly be of any use to anyone in fighting – whatever those creatures last night had been.

"They're called 'the Heartless'," he reported, reading off of the files that he had drawn up on his PDA. "One of my sources says that they come out of the darkness in peoples' hearts, while another says that they _are_ the darkness in peoples' hearts. The two kinds that ambushed us last night were Shadow Heartless and Soldier Heartless – the two weakest types out there. There are many other worlds out there, but no one knows exactly what world the Heartless first originated from, however, what is known is that they travel between the worlds and consume the hearts of those who succumb to the darkness. They ally themselves with whoever has a stronger heart of darkness."

"So now, we need to find out exactly who is controlling them." Valerie deduced.

"Well, we can immediately rule out the Box Ghost." Danny joked, much to the amusement of the rest of Team Phantom.

"Not Ember or Youngblood, I don't think," Sam reached her own conclusion. "Youngblood because, well, he's too young, really all he wants is to get rid of the adults. If he wants to get rid of adults, why attack the kids? And I think we can rule Ember out because she's not really evil, she just wants to be remembered. Granted, she's using a rather morally wrong way to do so, but I think that if she wasn't trying to hypnotize everybody whenever she visits, I think she would actually be a good ally."

"Would it be Desiree?" Tucker asked. "She used my jealousy of Danny against me when we first fought her."

"Possibly," Danny mused. "Another option might be Skulker; sending dark creatures and having them consume my heart would be a rather effective way to acquire my pelt, so that it can hang on his wall. It still can't be Vlad, because, like I said last night, he's still too much of a fruit-loop, and, last we checked, he's still in exile in space, though I might not put it past him to return if and when he hears about these things going on."

"There's also another option we haven't considered." Sam interjected. "What if it's not a ghost controlling the Heartless that attacked us last night. What if it was a human, one who we've run into before? Now..." she held up her hands to stop the others before they could object. "I know that pretty much all our enemies are ghosts. However, Freakshow was human, and, you never know, it could have been the Guys in White trying to catch Danny again."

"Freakshow used the Reality Gauntlet to turn himself into a full ghost the last time we fought, and the Guys in White keep off our backs, so long as I send them samples of my ecto-blood every couple of months." Danny explained. "Although, it could possibly be them using my ecto-blood samples to do experiments, things go wrong, and the Heartless are the result."

Screams erupted from outside, from the direction of the park.

"Sounds like that's our cue!" Danny shouted, leaping up and turning into Danny Phantom, causing everyone in the vicinity to burst into cheers as the four heroes took off in the direction of the screams.

"Sheesh, you'd think that, after this town's been attacked by ghost for nearly two years, you'd think that people would have grown used to sudden appearances made by supernatural creatures." Valerie commented, causing dry chuckles among her teammates.

However, when they got to the park, they found out that the attack wasn't from any ghost whatsoever, but from some more of the Heartless.

"Careful, guys," Tucker warned. "Looks like these guys are Deserter and Sergeant Heartless! They're a few steps up from those Soldier Heartless we fought last night."

"Well, then," Valerie declared, firing up her ecto-gun. "Let's give them a proper welcome!"

However, not only were these new Heartless more advanced than the ones last night, so that they were more resilient, but they were also smarter. A group of them split off from the main formation and headed for the main town. Valerie, thankfully, caught this and motioned to the team that she was going off to chase them and, hopefully, eliminate them before they caused any serious trouble in the town square.

Well, that was her plan, anyway; she was thankful that Amity Park citizens were smart enough now to avoid a new enemy, especially if it was one that even the famed Danny Phantom didn't know the origins of. As it was, even these things wouldn't immediately fall back after blasting them with her ecto-gun. Oh, she fired shot after shot, but after a while, her arms began to get tired from having to be held up for so long and from being in constant motion in order to ward off the Heartless from her.

The Red Huntress screamed in shock as more Heartless snuck up behind her and pulled her hover board down, causing her to lose her balance and fall, rather unceremoniously and painfully to the ground. The Heartless took that as their cue to descend upon her clawing at her, trying to touch her heart, turn it to the darkness at then consume it. Valerie tried using her guns, but the Heartless were quick to pin her arms down. For the first time since she started ghost hunting, Valerie was very, very afraid, but she didn't let it show. Instead she stared up, wanting the last thing she saw to be the blue sky.

Suddenly, the evil weight on her arms was lifted. Valerie quickly sat up to see her savior, expecting to see Tucker, or maybe Sam, but instead she saw a man that she had never seen before, not even anywhere around town. His long silver hair alone made him stand out slightly, but if his hair and clothing style didn't give him away as an outsider, his sword did. Shaped like some sort of giant key with an angel and demon wing design, he used it to slice through the Heartless as if they were nothing. Valerie had to admire this man's skill, but she also slightly resented the ease which with he took the Heartless out.

Before she had much time to become too shocked, all the Heartless had either been taken out by the man or had fled in terror of him, and Valerie was startled to see that his weird key-sword... thing disappeared as soon as he confirmed that the Heartless were gone. Seeing that part of his task done, he turned to the Red Huntress.

"Are you okay?" he asked her, holding out his hand to help her up, like a proper gentleman.

"_Wow,"_ Valerie thought. _"Not only does he have mean sword skills, he is also a gentleman and has a voice that would cause most girls to faint if it was directed at them._ However, Valerie was not most girls, and she graciously accepted his hand and allowed him to help her up. "You know, I had this handled," she said to him, trying to maintain at least SOME semblance of dignity.

"Right," the man laughed. "And I'm sure that 'having it handled,' as you put it, involved you pinned to the ground by a bunch of Heartless and about to have your heart consumed by darkness and you turned into one of them." Valerie huffed in indignation, quickly forgetting any notions that she may have been slightly attracted to him. "Name's Riku, by the way."

"Valerie," the Huntress responded. She may have thought that he seemed rude, arrogant, and sarcastic, but that didn't mean that she had to be rude right back to him. No, she would represent her city well and be polite. "I'd better get back to my friends; they were fighting more of those Heartless," she explained, reactivating her hover board. "They still probably need help. Want a lift? You're pretty good in a fight with those things; we could use your help."

"That's why we're here," Riku told her, accepting her hand this time and gracefully swinging onto the hover board behind her. "My friends and I fight Heartless for a living."

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After Valerie had left, more Heartless started arriving by the dozen. One managed to rake its long claws down Sam's arm, causing her to cry out in shock and pain, and causing Danny to start attacking more relentlessly, just to make sure that they didn't get ahold of her heart. Goth and gloomy she might be, but Danny was certain that she was NOT going to have her heart consumed by these monsters.

A _swoosh_ sound came from behind Danny, causing him to whirl around in shock. A white key-sword was right there, tendrils of darkness swirling around it briefly, signifying that it had just taken out a Heartless. The man holding onto the sword didn't really look anything like a hero (especially with that crazy hair!), but the confident, and more-than-slightly cheeky grin on his face left no doubt that he knew what he was doing. Another one of those keys, black this time, appeared in his other hand, and after winking at the red-haired woman who had arrived with him, both of them leaped into battle, their moves perfectly synchronized.

"I think I'm in love!" Tucker declared, watching the redhead.

Apparently, she heard him. "Sorry!" she laughed, taking time off the battle to flash him her left hand – or, more specifically, the diamond ring resting on the third finger of her left hand. "I'm engaged... to him," she finished, cocking her head in the spikey-haired man's direction. She gave one final giggle before turning back to the fight.

The Heartless, if it was at all possible, showed genuine fear at the sight of the couple, most fleeing almost immediately, and the rest were quickly cut down.

The two newcomers were tense for a moment, then dismissed their weapons, confident that the Heartless, for now, were gone. They turned to the three members of Team Phantom with friendly smiles.

"Sorry for the intrusion," the man said, "but, from our point of view, it looked like you guys needed a little help."

"Did we ever!" Sam agreed, still clutching her arm from where the Heartless had scratched her. "Thank you."

"Here, let me take a look at that." The woman held out her hand towards Sam's injury. Danny quickly wrapped his arms around his girlfriend, untrusting of these two strangers. Yes, the strangers had just saved their lives, but they knew next to nothing about these strangers. Who was to say that they only killed the Heartless just so that they could kill the team themselves? The woman sensed this and her smile turned more comforting. "It's all right; you can trust us."

That seemed to be enough for Sam, and she extended her arm to the woman, who summoned her own golden key again and placed it so that it was hovering over Sam's wound. "Heal," she murmured, causing a green light to encase Sam's arm and heal the claw marks. The Goth gaped in awe as her injury was healed in a matter of seconds. "Woah!" she exclaimed. "Thanks!"

The redhead grinned. "You're welcome. My name's Kairi and this is my fiancé, Sora." Sora gave a two-fingered salute. "We have another friend with us named Riku, who should be here any moment..."

Valerie chose that moment to come back, with said fellow arrival riding behind her on her hover board. "Speak of the devil," Sora muttered.

"How are you two engaged already?" Tucker asked, a little bit annoyed at the way she had simply blown him off. "You don't look much older than we are, and we're all fifteen."

"Look being the operative word." Sora laughed. "Kairi and I are both nineteen, and Riku's twenty."

"Well, I guess it's time for our introductions," Danny declared, transforming back into his human self, and delighting in the shock that registered on the three newcomer's faces. "Human form, I'm Danny Fenton, but in my ghost form, I go by Danny Phantom. These are my ghost-fighting team, Sam Manson, Tucker Foley, and Valerie Grey." He laughed again. "And I think I've got some explaining to do with the whole half human/half ghost thing."

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**A/N: Just couldn't resist having that thing with Tucker and Kairi, because we all remember how Tucker thought he was a bit of a ladies' man. And with Kairi and Sora being engaged, well, it had to happen sometime.**


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